In recent years, the widespread of color image apparatuses such as a digital camera, a scanner, a printer, and a display increases the chance for handling a color image by general people.
Conventionally, a specialist for color adjustment performs the image processing by an experimental technology in a closed system. Unlike the conventional image processing, the accurate use of a color image in an open system by the general people needs the color reproduction information having a common format or interface which defines the color reproduction property of an input/output device and a system for color conversion using the color reproduction information.
ICC (International Color Consortium) proposes Color Profile (hereinafter, referred to as an ICC profile) as the color reproduction information so as to realize a system for accurately managing and reproducing the color in the open system. The specification of the ICC profile is described in Specification ICC. 1: 1998-09 (document 1) (refer to http://www.color.org).
The ICC profile uses an XYZ or LAB color space prescribed by Commission Internationale de l'Eclairage (CIE) as an interface, namely, Profile Connection Space (PCS), and realizes the accurate transmission of the color information by signal processing via the PCS between different apparatuses.
The XYZ or LAB color space used as the PCS is embodied only under the observation environment of D50 illumination light prescribed by the CIE. The use of the XYZ or LAB color space under the restricted observation environment defines the PCS as a value indicating the color appearance.
A large part of the currently-widespread color image apparatuses and color reproduction systems use three primary colors. The specification of the ICC profile is basically prescribed based on the three primary colors, and the three-dimensional color space is used as the PCS, so as to transmit and reproduce three-dimensional color information.
On the other hand, the research and development advances into a multi-band camera for inputting an image by the number of bands not less than four bands, a multi-primary-color display device having four or more primary colors, and a multi-color printer.
In the color estimation using the multi-band camera, not only the color of a subject is accurately estimated but also the spectrum is accurately estimated. Thus, the color is estimated under arbitrary illumination light.
The color estimation from a photographing signal by using the multi-band camera is disclosed in the article “Development of color imaging system for accurate color reproduction” written by Yuri MURAKAMI et al. (on pages 5 to 8 of the collected papers “Color Forum JAPAN '99”) (document 2).
The multi-primary-color display is disclosed in “Six-Primary Color Projection Display for Expanded Color Gamut Reproduction” written by T. Ajito et al. (on pages 135 to 138 in Proc. Int. Symp. on Multispectral Imaging and Color Reproduction for Digital Archives, Chiba University, Japan, 1999) (document 3), in which the color area for reproduction is expanded. Furthermore, as disclosed in “Aspects of total multispectral image reproduction systems” written by B. Hill (on pages 67 to 78 in Proceedings of Second International Symposium on Multispectral Imaging and High Accurate Color Reproduction) (document 4), the multi-primary-color display can accurately reproduce the color for many people in views of the individual differences of perceiving a color matching function.
In addition, the multi-color printer is disclosed in “Spectral Color Reproduction for Hardcopy System by using Vector Error Diffusion Method” written by M. Kouzaki et al. (on pages 106 to 109 in Proceedings of Second International Symposium on Multispectral Imaging and High Accurate Color Reproduction) (document 5), in which a technology is described for reproducing the spectral reflectance by the hardcopy, thereby reproducing the same spectrum and color as those of the actual subject under arbitrary observation illumination-light.
As mentioned above, individual research reports exist with respect to the color reproduction technology via the spectral space using color-image input means or color-image output means such as multi-band input, the multi-primary-color display, and multi-color printing. However, a profile for prescribing the spectrum information necessary for color reproduction and means for realizing the color reproduction via the spectral space as an open system using the profile such as the color reproduction system using the ICC profile, has not been proposed.
Further, in these systems, a technology for spectral space expressed by the number of dimensions including the current three-dimensional color space and a system having compatibility with the current system are requested.
The present invention is devised in view of the above circumstances and it is one object of the present invention to provide a spectrum and color reproduction system capable of accurately reproducing the spectrum or color of the color image inputted by the color-image input means.
Further, it is another object of the present invention to provide a spectrum and color reproduction system which enables the compatibility with the current color reproduction system via the three-primary-color space.